# instantaneous frequency

Also found in: Acronyms.

## instantaneous frequency

[¦in·stən¦tā·nē·əs ′frē·kwən·sē]
(communications)
The time rate of change of the angle of an angle-modulated wave.
References in periodicals archive ?
3) enables us to represent the amplitude and the instantaneous frequency as functions of time in a threedimensional space.
The instantaneous frequency amplitude of MFSK signals after wavelet transform can be approximated as followed:
Step 2: Use LMD method to decompose the purified signal into PFs, meantime instantaneous amplitude and instantaneous frequency of each PF component can be calculated.
For a multicomponent signal, the instantaneous frequency defined by the Hilbert transform is not necessarily a single-valued function of time [26].
Therefore, in order to choose the appropriate t-f points, it is necessary to mitigate cross-terms in TFDs and obtain the instantaneous frequency of signal.
The interference will take on spikes in instantaneous frequency spectrum.
Instead, the parameter [theta], which is an estimate of the instantaneous frequency of the moving target, is integrated to generate the phase response of the matched filter.
The various features of the modulation schemes that are identified in this step include instantaneous frequency, bandwidth, occupation time and duration of occupation of each occupied slot.
Generally, a sine-wave chirp signal with instantaneous phase [theta](t) can be described mathematically as c(t) = sin([theta](t)) = sin(2[pi][integral]f(t)dt), instantaneous frequency of which changes in time as f(t) = (d[theta](t)/dt)/2[pi].
Comprising two aerial assemblies, an electronics unit and a cockpit display and control panel, the TDS-FA/Aigle is further claimed to offer a 'very short' reaction time and 'highly dependable' emitter identification based on instantaneous frequency measurement.
Recently, a new signal detection methodology was developed, based on the application of instantaneous frequency measurement (IFM), integrated with commercial processors that permit simultaneous detection, monitoring, and tracking of RF signals (continuous wave, pulsed, and transient) at frequencies from 0.

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